CONSTRUCTION OF 3-D MODELS OF LITHOSPHERIC STRUCTURE: A SCHEME FOR INTEGRATION OF GEOPHYSICAL DATA

A fundamental goal of geophysical studies of the lithosphere is to characterize the 3-D structure of a region of interest in order to address key scientific questions. This could be accomplished by determining physical properties such as Vp, Vs, density, magnetic properties, electrical properties, anisotropy, attenuation (Q), temperature, etc. for volume elements that could take several forms. In addition, interfaces that represent features such as the Moho, faults, magmatic bodies, etc. must also be be mapped in order to properly characterize a region. This goal can only be achieved through a highly integrated approach that takes advantage of all of the geological and geophysical constraints available. In most cases, controlled source and passive seismology have the potential for providing the greatest resolution, but generally are the mostly costly approaches. Furthermore, many diverse techniques are available for each data type collected. Thus, developing an integration scheme for seismic results is an important first step in reaching our fundamental goal. Each data type has its own sensitivities and resolution, and when used alone can constrain some aspects of the lithospheric structure. However, when used together with other data sets, the joint data sets have the potential for constraining fundamental aspects of the lithospheric structure. For example, controlled source experiments can yield the Vp structure, and sometimes Vs structure, of the crust and uppermost mantle while passive source experiments can constrain the Vp/Vs ratio with a receiver function analysis that utilizes full-crustal reverberation(s) from teleseismic earthquakes. Thus together, they can provide a relatively high resolution, full seismic model of the crust and upper mantle. Potential field data can also help constrain our lithospheric models. For example, gravity data are available in most regions and, due to the approximate physical relationships between density and seismic velocity, have long belong employed as at least as a qualitative check on seismic results particularly in the lithosphere. Formal integration has been attempted in many ways over the years, but some recent 3-D approaches are ideally suited for at least joint modeling that provides better overall models of lithospheric structure.